A co-frequency full-duplex technology refers to a communication manner in which when a communications device performs wireless communication, transmitting and receiving are performed simultaneously, and signal transmitting and signal receiving use a same spectrum resource. Compared with a communication manner of time division duplex, in the communication manner of co-frequency full-duplex, signal sending and receiving can be performed simultaneously. Compared with a communication manner of frequency division duplex, in the communication manner of co-frequency full-duplex, signal sending and receiving can be performed by using a same spectrum resource. Therefore, in a same spectrum resource condition, a transmission speed of the co-frequency full-duplex technology is twice higher than a transmission speed of the time division duplex technology and a transmission speed of the frequency division duplex technology.
When a communications device performs co-frequency full-duplex communication, a transmitter of the communications device causes co-channel interference to a receiver. In the prior art, the communications device performing co-frequency full-duplex communication is generally disposed with a circulator. The circulator includes three ports, which may be defined as an antenna port, a receiver port, and a transmitter port, where the antenna port, the receiver port, and the transmitter port are connected to a transmit and receive antenna, the receiver, and the transmitter respectively. The circulator can increase isolation between the transmitter and the receiver, and decreases interference from the transmitter to the receiver.
In a process of implementing the present invention, the inventor finds that the prior art has at least the following problems:
In the foregoing structure in which the circulator is used, co-channel interference is caused due to mismatch of the antenna port of the circulator, and some of signals transmitted by the transmitter by using an antenna are reflected back to the circulator by the antenna and enter the receiver, which causes that interference from a transmit signal to a receive signal is relatively high.